Forty-four odor-active compounds were quantified in Scheurebe and Gewurztraminer wines, respectively. Calculation of odor activity values (OAVs) of odorants showed that differences in odor profiles...

Quantitation and Sensory Studies of Character Impact Odorants of Different White Wine Varieties

1H NMR methods employing very fast magic-angle spinning (MAS) are applied to the investigation of both the structure and dynamics of an alkyl-substituted hexa-peri-hexabenzocoronene (HBC), which is known to form a columnar mesophase with a very high one-dimensional charge carrier mobility. For the crystalline phase, three distinct aromatic resonances are identified in the single-quantum MAS spectrum. The observation of these distinct aromatic resonances is explained in terms of the differing degrees to which the aromatic protons experience the ring current of adjacent layers. Using the rotor-synchronized double-quantum MAS method, definite proton−proton proximities are identified, which are shown to be in agreement with the known crystal structure of unsubstituted HBC. In the liquid-crystalline phase, axial motion of the HBC disks leads to the averaging of the three sites into a single resonance. Furthermore, the reduction of the dipolar coupling caused by this motion is quantitatively investigated by an ...

An Investigation of pi-pi Packing in a Columnar Hexabenzocoronene by Fast Magic-Angle Spinning and Double-Quantum1H Solid-State NMR Spectroscopy

The design and synthesis of the first examples of AB4 and AB5 dendritic building blocks with complex architecture are reported. Structural and retrostructural analysis of supramolecular dendrimers self-assembled from hybrid dendrons based on different combinations of AB4 and AB5 building blocks with AB2 and AB3 benzyl ether dendrons demonstrated that none of these new hybrid dendrons exhibit the previously encountered conformations of libraries of benzyl ether dendrons. These hybrid dendrons enabled the discovery of some highly unusual tapered and conical dendrons generated by the intramolecular back-folding of their repeat units and of their apex. The new back-folded tapered dendrons have double thickness and self-assemble into pine-tree-like columns exhibiting a long-range 7/2 helical order. The back-folded conical dendrons self-assemble into spherical dendrimers. Non-back-folded truncated conical dendrons were also discovered. They self-assemble into spherical dendrimers with a less densely packed cent...

Expanding the structural diversity of self-assembling dendrons and supramolecular dendrimers via complex building blocks.

This contribution focuses on the hydrogenation and hydrodeoxygenation of aldehydes (benzaldehyde, 2-phenylpropionaldehyde, 3-phenylpropionaldehyde, cinnamaldehyde, 4-isopropylbenzaldehyde, heptanal) on supported palladium catalysts, namely zeolites and active carbon. The effects of the substrate structure, solvent, type of support and its acidity, reaction temperature and pressure on activity and selectivity of Pd catalysts were investigated in detail. Catalytic hydrodeoxygenation of aldehydes was carried out in a liquid phase in an autoclave in the temperature range from 30 to 130 °C and at pressure ranging from 1 to 6 MPa. Hydrogenation reactions performed in non-polar hexane proceeded with a significantly higher rate than in a polar methanol. The presence of isopropyl substituent in 4-isopropylbenzaldehyde increased both the reaction rate as well as the selectivity to hydrodeoxygenation. Hydrodeoxygenation of 2-phenylpropionaldehyde, 3-phenylpropionaldehyde, cinnamaldehyde, and heptanal did not proceed, the main products were dialkylethers, which evidences the importance of the direct attachment of C O group to the benzene ring. The presence of hydrogenation—hydrogenolytic mechanism as well as the direct hydrogenolysis of C O bond in the transformation of benzaldehyde was verified.

Hydrodeoxygenation of aldehydes catalyzed by supported palladium catalysts

Alanate (Metallaluminiumhydride) lassen sich aus den Elementen ein- oder zweistufig leicht und in guter Ausbeute synthetisieren. Vorzugsweise wird Natriumalanat zweistufig hergestellt, indem man aus natrium und Wasserstoff Natriumhydrid erzeugt und dieses mit Aluminium und Wasserstoff in Tetrahydrofuran weiter umsetzt. Aus dieser Losung last sich reines NaAlH4 mittels Diathylather fallen und solvatfrei gewinnen. Die Eigenschaften des Natriumalanats werden beschrieben und einige Anwendungsmoglichkeiten in der organischen und anorganischen chemischen Technik angegeben. Das weniger polare Lithiumalanat kann als Losung analog, aber noch wirtschaftlicher und frei von Losungsmitteln aus Natriumalanat und Lithiumchlorid durch Vermahlen in Ather hergestellt werden. Ferner wird u. a. uber die rationelle Herstellung anderer Alanate, des Aluminiumhydrids und des Silans sowie uber deren Verwendungsmoglichkeiten berichtet.

C. Rainer A. Berger

Papers

Reduction of Organic Compounds by Mixed Hydrides. II. Hydrogenolysis of Ketones and Alcohols1